The present invention relates to programmer/timers of the type having a plurality of switches actuated in a timed sequence for controlling the operation of the various functions of an appliance. Programmer/timers of this sort are typically employed for controlling the program cycle of appliances such as automatic clothes washers and dishwashers. Such programmer/timers for clothes washers and dishwashers commonly employ a program cam which is advanced in timed relationship, for example, by an advance mechanism powered by a small subfractional horsepower timing motor to sequentially actuate the various function switches.
In the aforesaid time programmer/timers for clothes washers and dishwashers, the cam is commonly configured as a rotary drum which is initially positioned for selecting the length of the program by user rotation of a knob attached to the shaft upon which the cam is mounted. In a particularly widely used arrangement of household clothes washers and dishwashers, the knob is disposed to be either pushed or pulled in the axial direction for permitting rotation and setting of the program cam upon movement of the knob in one axial direction and energization of the programmer/timer by movement in the opposite axial direction. Users have become accustomed to this mode of control operation and it has achieved widespread acceptance in the marketplace for household appliances.
Heretofore, in the design and manufacture of programmer/timers for appliances, problems have been encountered in locating and positioning the cam followers for accurate timed sequencing for the actuation of the various switches. The tolerances accumulated in the manufacturing of the cam, the locating of the cam for rotation on the programmer/timer housing or base, and the tolerances in manufacturing the individual cam followers and locating the followers on the programmer/timer base or housing have made it difficult to achieve the desired program accuracy with a cam drum sized to fit the volume envelope available for the programmer/timer. Furthermore, the tolerances accumulated in manufacturing the individual components and the assembly of the advance mechanism have caused inaccuracies in the actuation of the individual switches and variations in the incremental advance of the cam by the advance mechanism which in turn results in further timing inaccuracies of the switches. Thus, in designing and manufacturing electromechanical programmer/timers for appliances, and particularly those employing a plurality of switches actuated by a sequentially advanced cam, the problem of positioning the program cam with respect to the switches has been formidable in view of the tolerance accumulation of the parts and the fact that more than one reference datum is employed for locating the cam followers and switches with respect to the cam.
Thus, it has been long desired to provide a simplified construction for an electromechanical programmer/timer which eliminates the inaccuracies due to tolerance accumulation in locating the switches with respect to the program cam.
Furthermore, in the aforesaid type electromechanical appliance programmer/timers, where a single pole double-throw (SPDT) type switching is required for each switch, it has been found quite difficult to control the accuracy of the switching of the side contacts where a rotary cam is employed for actuating the cam followers and switches. Where a cam drum employs a single cam track for each switch, it has been found difficult to provide for accurate making and breaking of the side contact with the single cam track. Heretofore, in the aforesaid type programmer/timers, and particularly where an SPDT switching action is desired, only the center or common contact has been moved to accomplish the switching of the side contacts. This has resulted in certain inaccuracies of switching and for which it has been desired to eliminate.
Heretofore, programmer/timers of the aforesaid type which have employed a plurality of cam tracks on a cylindrical surface to form a cam drum against which a switch cam follower rides on each of plural cam tracks formed about the drum. In this type of switching arrangement, in order for an SPDT switch to function, the center or common blade must follow the movement of the cam follower and thus slide against the friction of the cam ramp, or up the cam, to effect closing of one of the side contacts with the common contact blade whereupon the accuracy of the switching is a function of the spacing of the side contact from the common contact blade. The amount of cam motion and time is thus determined by the limit of the slope of ramp. Where one revolution of the cam drum represents a full or complete appliance program cycle, this necessarily limits the frequency of switch actuation which can be obtained for a given size or diameter of cam drum, for a given rate of cam advancement. In addition, known electromechanical programmer/timers for appliances, particularly those employed for household clothes washers and dishwasher machines which employ a plurality of rotary cam actuated switches, have exhibited the unwanted characteristic of being noisy when the user moves the knob axially to rotate the cam for selecting the starting position and program interval time. This is because, as the cam is rotated, the followers are moved to mechanically actuate and deactuate the switches despite the electrically de-energized state of the programmer/timer. It has thus also been desired to provide an economical way to disengage the cam from the followers to eliminate the noise of the switch actuation and deactuation during setting of the program cam by the user.
It has thus been long desired to provide a design for an electromechanical appliance programmer/timer which eliminated the foregoing drawbacks and disadvantages.